 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.internal.services;

 import java.util.Comparator ;

 import org.eclipse.ui.internal.util.Util;

 /**
  * <p>
  * Compares two evaluation result caches ({@link IEvaluationResultCache}). The
  * cache with the lowest source priority is considered "greater". In the event
  * of a tie, other characteristics are checked.
  * </p>
  * <p>
  * This class is only intended for use within the
  * <code>org.eclipse.ui.workbench</code> plug-in.
  * </p>
  *
  * @since 3.2
  *
  */
 public final class EvaluationResultCacheComparator implements Comparator {

     public final int compare(final Object object1, final Object object2) {
         if (Util.equals(object2, object1)) {
             return 0;
         }

         final IEvaluationResultCache cache1 = (IEvaluationResultCache) object1;
         final IEvaluationResultCache cache2 = (IEvaluationResultCache) object2;
         int comparison;

         /*
          * Note: all of the comparisons are flipped intentionally. This allows
          * those items with greater values to appear earlier when using an
          * iterator.
          */
         // if objects went to the trouble to implement Comparable
 // we should use it ... this algorithm can accept a natural ordering
 // that's not compatible with equals.
 if (object1 instanceof Comparable && object2 instanceof Comparable ) {
             comparison = Util.compare((Comparable ) object2,
                     (Comparable ) object1);
             if (comparison != 0) {
                 return comparison;
             }
         }

         return Util.compareIdentity(cache2, cache1);
     }
 }


